<br />    
<div class="container">
            <div class="center-block logig-form">
                <div class="panel panel-default">
                    <div class="panel-heading">Formulário de Login</div>
                    <div class="panel-body">
                      <?php $atributos_formulario = array('id'=>'exm1','role'=>'form','onsubmit'=>'PreventMultipleSubmit()');
                            echo form_open ("administracao/principalcontroller/logar",$atributos_formulario);
                            if(validation_errors())
                            {   echo '<div class="alert alert-danger">
                                <button type="button" class="close " data-dismiss="alert">&times;</button>
                                <span>'.validation_errors().'</span>                                    
                                
                                    
                                </div>';
                            }
                            if(isset($mensagem))
                            {   echo '<div class="alert alert-danger">
                                <button type="button" class="close " data-dismiss="alert">&times;</button>
                                <span>'.$mensagem.'</span>                                    
                                
                                    
                                </div>';
                            }?>
                            <div class="form-group">
                                        <div class="input-group login-input">
                                         
                                            <span class="input-group-addon"><i class="fa fa-user"></i></span>
                                            
                                             <?php echo form_input(array('name'=>'email', 'type'=>'email','class'=>'form-control','placeholder'=>'Digite seu Email','required'=>'required'),  set_value('email'));?>
                                              
                                        </div>
                                        <span>Digite seu email</span>
                                        <br>
                                        <div class="input-group login-input">
                                             
                                            <span class="input-group-addon"><i class="fa fa-lock"></i></span>
                                            
                                            <?php echo form_input(array('name'=>'cpf','id'=>'cpf','type'=>'text','class'=>'form-control','placeholder'=>'Digite seu CPF','required'=>'required'),  set_value('cpf'));?>
    
                                        </div><span>Digite seu cpf</span><br />
                                       <?=br(3);?>
                                        <button type="submit" id="btSubmit" class="btn btn-primary pull-right">Enviar</button>
                                       
                                         <?php 
                                    $image_properties = array(
                                    'src' => 'img/loading.gif',
                                    'alt' => 'avatar',
                                    'class' => 'img-responsive imageborder x',
                                    'width' => '104',
                                    'height' => '45',
                                    'title' => '',
                                    'id' => 'carregando',                                    
                                    );                                    
                                    echo img($image_properties);?>
                                        
                                        <div class="clearfix"></div>
                                    </div>
                        <?php echo form_close() ?>
                    </div>
                </div>
            </div>
        </div> <!-- container  -->